Privacy policy
Your saved words and review history are stored in your browser. Hakkutsu has no user accounts or analytics tracking. Below is a guide to storage, permissions, and connections.
No activity tracking
No Google Analytics, Sentry, Mixpanel, or telemetry pings. We collect zero user events.
No registration required
No registration, no email capture, no passwords, and no cloud synchronization tokens.
Saved on your device
Mined vocabulary, FSRS parameters (D, S, R), and offline JMDict live in your browser sandbox.
Export to your desktop
AnkiConnect requests communicate strictly with your local desktop Anki software upon user export.
01 What Hakkutsu does
Hakkutsu is an open-source Japanese language immersion toolkit created to assist language learners with reading Japanese webpages, following subtitle-annotated streaming videos, recognizing raw manga speech bubbles, and reviewing flashcards.
All computational processing is performed locally on your personal computer. Hakkutsu does not require an account, collects zero Personally Identifiable Information (PII), and operates without any remote cloud backend infrastructure.
02 What is stored
All data generated or utilized during your immersion sessions is stored strictly within your browser's local sandbox:
- Vocabulary & SRS Database (hakkutsu-srs in IndexedDB) Stores mined cards, context sentences, timestamps, audio clips, screenshots, and FSRS-4.5/5 scheduling parameters: Difficulty D, Stability S, Retrievability R, repetition history, and lapse counts. This database is never synced to external servers.
- Offline Dictionary Database (HakkutsuDictDB in IndexedDB) Stores local JMDict bilingual definitions, pitch accent patterns, and kanji stroke order paths to power instant offline word lookups without network delay.
- User Preferences (chrome.storage.local / sync) Stores user-configured hotkeys, target retention rate preferences, selective furigana JLPT filters, theme modes, and UI language selections in standard browser storage.
03 When connections happen
Hakkutsu does not transmit any user telemetry, reading statistics, or vocabulary cards to external servers. The only network interactions that may occur are:
- Local AnkiConnect Bridge: When you click "Export to Anki", Hakkutsu sends an HTTP POST request to http://127.0.0.1:8765 on your local machine. This communication is strictly between your browser and your local Anki desktop software.
- Audio Pronunciation: Japanese speech audio utilizes the built-in browser Web Speech API (offline) or user-configured endpoints. No audio recordings are ever collected or uploaded.
04 Browser permissions
Hakkutsu requests only the minimal browser permissions necessary to provide in-page immersion tools:
| Permission | Technical Scope & Purpose |
|---|---|
| storage | Stores user configuration, review preferences, and offline dictionary cache locally. |
| tabs | Reads the active video tab URL and page title to attach source attribution to mined flashcards. |
| activeTab | Allows inspecting selected Japanese text when opening the toolbar quick-lookup popup. |
| scripting | Injects lightweight HTML5 video detection helpers to synchronize subtitle tracks on YouTube and Netflix. |
| offscreen | Runs Tesseract OCR in an isolated background document to detect manga speech bubbles without freezing the UI. |
| https://*/* | Enables inline dictionary lookups, selective furigana, and subtitle overlays across Japanese web content. |
| http://127.0.0.1:8765/* | Connects to local AnkiConnect desktop bridge on loopback port 8765 for 1-click card export. |
05 Other software
Hakkutsu integrates with third-party software strictly through user-directed, local mechanisms:
- Anki Desktop Software: All Anki card generation uses the local AnkiConnect add-on over loopback. You remain in complete control of your Anki decks, tags, and media collections.
- Web Speech API: Pronunciation playback leverages the operating system's native text-to-speech synthesizer where available. No third-party TTS audio service receives user text.
06 Export, backups & deletion
Because all data is stored on your device, you retain total ownership:
- Full JSON Backup: Export your entire vocabulary collection, review intervals, stability factors, and difficulty metrics into a portable JSON file under Dashboard → Backup.
- Standard CSV Export: Export mined vocabulary to standard CSV format for importing into spreadsheets or external flashcard programs.
- Permanent Deletion: Uninstalling the extension or clearing your browser's site storage instantly and permanently purges all local IndexedDB stores and preferences.
07 Verify it yourself
We believe privacy should be verifiable, not merely promised. Any user or security researcher can audit Hakkutsu's network activity in real time: